linux-kernel - Re: [PATCH 27/32] gpio: Add support for the FXL6408 GPIO expander.

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Date:	Wed, 8 Jun 2016 11:10:58 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Gerd Hoffmann <kraxel@...hat.com>
Cc:	linux-rpi-kernel <linux-rpi-kernel@...ts.infradead.org>,
	Eric Anholt <eric@...olt.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Alexandre Courbot <gnurou@...il.com>,
	"open list:BROADCOM BCM281XX/BCM11XXX/BCM216XX ARM ARCHITE..." 
	<bcm-kernel-feedback-list@...adcom.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@...r.kernel.org>,
	"moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
	<linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH 27/32] gpio: Add support for the FXL6408 GPIO expander.

On Wed, Jun 1, 2016 at 11:43 PM, Gerd Hoffmann <kraxel@...hat.com> wrote:

> +#define FXL6408_OUTPUT                 0x05
> +/* Bits here make the output High-Z, instead of the OUTPUT value. */
> +#define FXL6408_OUTPUT_HIGH_Z          0x07
(...)
> +       /* Disable High-Z of outputs, so that our OUTPUT updates
> +        * actually take effect.
> +        */
> +       i2c_smbus_write_byte_data(client, FXL6408_OUTPUT_HIGH_Z, 0);

High-Z is probably the same as open drain right? And if not open drain,
it is push-pull.

So you want to implement .set_single_ended() for configuring the lines in
"high-z", i.e. open drain output mode.

Yours,
Linus Walleij